In support documents for the forthcoming LG UltraFine 5K display published on Tuesday, Apple notes older Mac models, including 2013's Mac Pro, can be used at 4K resolution screen when connected via a Thunderbolt 3 to Thunderbolt 2 adapter. 

Meanwhile Apple and LG are pitching their final on sale UltraFine 5K display at owners of the 2016 MacBook Pro, some of the owners are confused and wondering whether it will be compatible with their machines or not. The answer is no but on the other side Apple support documents claims that it is kind of compatible with some older machines too.

According to 9to5mac the Apple's Support Pages documents shows that the new LG display can hit 5K resolution with Thunderbolt 3-equipped computer running macOS Sierra 10.12.1 or later.

Only the 2016 MacBook Pro models can drive the display at its full 5120×2880 5K resolution. This is to be Retina version of 2560x1440 of the now discontinued Apple Thunderbolt Display-pixels doubled in both the X and Y axes to provide that 'cannot discern the individual pixels' quality. 

As per Appleinsider the latest MacBook models are also the only ones that can be powered by the monitor providing a single cable connection.  On the other side display is compatible with Thunderbolt 2 machines but at a lower resolutions, documents suggest that users need buy the Apple Thunderbolt 3 USB-C to Thunderbolt 2 Adapter and a Thunderbolt 2 cable for using the new screen.

LG UltraFine is only recommended as a second display, as it may not turn on until booted into macOS, which mean user will not get the access to Boot picker or macOS Recovery Mode.

As far as power concern the power delivery feature allows the UltraFine monitor to charge teh MacBook by only using one cable, also available in 2016 MacBook Pro lineup featuring with Thunderbolt 3.0 ports.

Now what about pricing, as per Apple's online store the LG UltrFine 5K will cost USD 975, and will be estimated to deliver in 3-4 working days to 2-4 weeks, due to delay in launching the monitor Apple has went ahead and discounted the promotional pricing from USD 1299 to USD 975 till March 31st.